Hearing protectors of the kind mentioned above are utilized to a very great extent by persons who must spend a lot of time in noisy environments. It is very important that the hearing protector is experienced as comfortable to wear, since it will otherwise easily be "forgotten" with the accompanying risk of injury. An example of a hearing protector of this kind is described in our U.S. Pat. No. 3,908,200. Another example is described in EP-A1-127,275.
From the sound damping aspect it is essential that the earmuff sealing ring engages closely against the head everywhere round the ear. From the comfort aspect it is further essential that the sealing ring is soft and pliable and adjusts itself well to the shape of the head in a pressure--equalizing manner. With these conditions in mind the sealing ring has for a long while included foamed plastics material inside the sealing ring sheath. The foamed plastics material has very good flexibility and is furthermore light, which gives low weight of the hearing protector, something which is also of essential importance from the comfort aspect.
However, a foamed plastics-filled sealing ring has the property of being a good "heat insulator", and it therefore easily becomes unsatisfactorily "hot" where the ring engages against the head. Liquid-filled sealing rings have been proposed in an attempt to solve this problem. The liquid provides a cooling effect which is experienced positively by many. Filling with liquid also involves problems, however, since the weight of the hearing protector increases substantially and since requirements for leak proof and puncture--proof nature of the sealing ring sheath increase. Some persons also experience the liquid-filled sealing rings as less soft and comfortable than the formed plastics filled sealing rings. It has also been found that the liquid-filled sealing rings have not come to be as dominating as was expected.